On Tue, Jun 12, 2012 at 3:31 PM, Ask Bjørn Hansen <[email protected]> wrote: > On Jun 11, 2012, at 19:29, Timothy Oefelein <[email protected]> wrote: > >> 1) What kind of accuracy/precision loss occurs when you run ntpd on an >> asymmetrical connection (e.g., DSL). I've read that ntpd makes the >> assumption that your connection is symmetrical when calcuating the effects >> of network latency. One of my servers is on an ADSL connection, hence the >> question. > > As long as the connection isn't loaded so packets get buffered, it is > basically fine.
For a NTP server synchronized to external NTP servers over the DSL, the offset error due to the asymmetric delay of the DSL cancels out for WAN clients of that server. However, if your NTP server is synchronized via GPS+PPS, the error is not cancelled for WAN clients. On a Frontier 3M/768k DSL with the default configuration (interleaved), the error is close to 7 milliseconds. Enough that I don't join that host to the pool, as it has local clients as well and I don't want their time off by 7 msec, which would be the effect if I were to fudge the refclock time so my NTP server's offset appeared aligned with other public NTP servers to clients on the internet. For some people, 7 msec is nothing. For me, it's unacceptable. Cheers, Dave Hart _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
